The present invention relates to the magnetic resonance art. It finds particular application in conjunction with a method and apparatus for mounting a gradient tube to a magnetic resonance imaging (MRI) device and will be described with particular reference thereto. However, it should be appreciated that the present invention may also find application in conjunction with magnetic resonance spectroscopy systems and other applications which utilize gradient tubes.
In magnetic resonance imaging applications, three orthogonal gradient fields are employed to provide spatial resolution by frequency discrimination of an MRI signal. A gradient tube typically includes three discrete gradient coils for generating the x, y, and z-gradient fields. The discrete coils are insulated from each other and are layered on a cylindrical former. Commonly, the entire gradient tube is overwrapped and epoxy impregnated for greater structural strength.
A self-shielded gradient tube typically includes a secondary or shielding gradient coil set spaced radially from a primary gradient coil set. The primary and secondary gradient coil sets each include insulated coils for generating x, y, and z-gradient fields which can be layered on separate cylindrical formers or on a single unitary former.
Both types of gradient tubes must be constrained in the x, y, and z directions when mounted within the cylindrical bore of an MRI magnet housing due to the magnetic forces acting on the gradient tube. The gradient tube is typically secured to the magnet housing by mounting rings positioned at both ends of the cylindrical bore to, in effect, trap the gradient tube between the mounting rings. However, the mounting ring design makes the front tunnel liner design much more claustrophobic from the patient's perspective, in addition to limiting access to the patient by medical personnel. Further, mounting rings interfere with service-end water headers on liquid-cooled gradient tubes making the designs complex and costly.
In an alternative arrangement, the gradient tube can be mounted to tombstone-like castings secured to the floor and located at the patient and service-ends of the magnet housing. However, the tombstone gradient tube mounts make the MRI device substantially longer, making access to the patient more difficult.
The present invention contemplates a new and improved method and apparatus for mounting a gradient tube to an MRI device which overcomes the above-referenced problems and others.